The first time I saw the "skip" option, I thought I was opting to skip on a book-by-book basis, but no, it ended the entire sync process. There is a caveat, if you end the process, but have your WiFi turned on, after the reader reboots as the update happens, the books will download. For that reason, if you really don't want the books to download onto your device, do NOT have WiFi going at the time. After that, just don't sync if there are books in I'm Reading on the desktop or on the website.